Heterogeneous spectroscopic transceiving photonic integrated circuit sensor

ABSTRACT

Described herein are optical sensing devices for photonic integrated circuits (PICs). A PIC may comprise a plurality of waveguides formed in a silicon on insulator (SOI) substrate, and a plurality of heterogeneous lasers, each laser formed from a silicon material of the SOI substrate and to emit an output wavelength comprising an infrared wavelength. Each of these lasers may comprise a resonant cavity included in one of the plurality of waveguides, and a gain material comprising a non-silicon material and adiabatically coupled to the respective waveguide. A light directing element may direct outputs of the plurality of heterogeneous lasers from the PIC towards an object, and one or more detectors may detect light from the plurality of heterogeneous lasers reflected from or transmitted through the object.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/545,362, filed Aug. 20, 2019, which is a continuation of U.S.application Ser. No. 16/162,489, filed Oct. 17, 2018, which is acontinuation of U.S. application Ser. No. 15/723,409, filed Oct. 3,2017, which is a continuation of U.S. application Ser. No. 14/865,318,filed Sep. 25, 2015, which claims the benefit of priority to U.S.Provisional Patent Application Ser. No. 62/056,765, filed Sep. 29, 2014,all of which are hereby incorporated herein by reference in theirentirety.

FIELD

Embodiments generally pertain to optical devices and more specificallyto optical sensing components included in photonic integrated circuits.

BACKGROUND

Spectroscopic sensing processes for chemical analysis of substances andnoninvasive measurements of blood constituents has long been proposedfor detection and health monitoring. Laser based systems providesubstantially higher signal to noise; however due to the large size andcost of laser based spectroscopic systems, they are not routinelydeployed.

Spectroscopic systems that are based on discrete laser sources and basedon the limited wavelength range of semiconductor sources are too largeand too expensive for several uses, including spectroscopic sensing viawearable health monitoring devices. Spectroscopic systems utilizingbroadband sources also utilize a spectrometer on the detector side,which increases system size and weight and decreases the efficiency oflight collection.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description includes discussions of figures havingillustrations given by way of example of implementations and embodimentsof the subject matter disclosed herein. The drawings should beunderstood by way of example, and not by way of limitation. As usedherein, references to one or more “embodiments” are to be understood asdescribing a particular feature, structure, or characteristic includedin at least one implementation of the disclosure. Thus, phrases such as“in one embodiment” or “in an alternate embodiment” appearing hereindescribe various embodiments and implementations of the disclosure, anddo not necessarily all refer to the same embodiment. However, suchphrases are also not necessarily mutually exclusive.

FIG. 1A-FIG. 1C illustrate components a photonic integrated circuit usedfor optical sensing in accordance with some embodiments.

FIG. 2A-FIG. 2B illustrate cross-section and top-down views ofcomponents of photonic integrated circuits used for optical sensing inaccordance with some embodiments.

FIG. 3 illustrates a cross-section view of components of a photonicintegrated circuit used for optical sensing in accordance with someembodiments.

FIG. 4 is a flow diagram of a process for operating an optical sensingdevice in accordance with some embodiments.

FIG. 5 is an illustration of an arrayed waveguide grating used for anoptical sensing device in accordance with some embodiments.

Descriptions of certain details and implementations follow, including adescription of the figures, which may depict some or all of theembodiments described below, as well as a description of other potentialembodiments or implementations of the concepts presented herein. Anoverview of embodiments is provided below, followed by a more detaileddescription with reference to the drawings.

DESCRIPTION

Embodiments of the disclosure describe optical sensing devices forphotonic integrated circuits (PICs). Throughout this specification,several terms of art are used. These terms are to take on their ordinarymeaning in the art from which they come, unless specifically definedherein or unless the context of their use would clearly suggestotherwise. In the following description, numerous specific details areset forth to provide a thorough understanding of the embodiments. Oneskilled in the relevant art will recognize, however, that the techniquesdescribed herein can be practiced without one or more of the specificdetails, or with other methods, components, materials, etc. In otherinstances, well-known structures, materials, or operations are not shownor described in detail to avoid obscuring certain aspects of thedisclosure.

FIG. 1A-FIG. 1C illustrate components a photonic integrated circuit(PIC) used for optical sensing in accordance with some embodiments. APIC 100 is illustrated as an optical transceiver device and is shown toinclude several components on the transmitter portion 110 and thereceiver portion 120 of the PIC. As described in further detail below,the transmitter portion 110 of the PIC 100 is to emit light towards amedia for sensing 190, while the receiver portion 120 of the PIC 100 isto receive light from (e.g., reflected from or transmitted through) themedia for sensing 190.

The transmitter portion 110 is shown to include a light source array112, a modulator array 114, a transmit coupler array/aperture 116, and atransmission optical element 118. In some embodiments the light sourcearray 112 may comprise a plurality of narrow band light sources, such asa plurality of lasers or a plurality of high power light emitting diode(LED) light sources. In some embodiments, the light source array 112 maycomprise tuning elements, such as a tunable filter, for tuning theoutput of the light source array 112 to emit over a wavelength range (inthis embodiment, wavelengths λ₁−λ_(N)) significantly wider than a singlesemiconductor media.

The modulator array 114 of the transmitter portion 110 of the PIC 100may be used to modulate the outputs of the light source array 110. Bymodulating the outputs of the light source array 110 (for example, atdifferent frequencies), their individual contributions that reach one ormore detectors (described in further detail below) can be determined byvarious techniques.

The modulated outputs of the light source array 112 are output from thePIC 100 via the transmit coupler array/aperture 116. In someembodiments, the transmit coupler array/aperture 116 comprises an arrayof optical couplers (e.g., one for each source) within an aperture. FIG.1B illustrates an alternative embodiment of a transmit couplerarray/aperture element 116B, wherein the modulated outputs of themodulator array 114 are received by an optical multiplexer 170, and thesingle output of the multiplexer is received by a single coupler 172.

Referring back to FIG. 1A, in this embodiment, the output of thetransmit coupler array/aperture 116 is received by the optical element118 prior to the light being received by the media for sensing 190. Theoptical element 118 may contain one or more elements for shaping theemitted light and directing the emitted light towards the media forsensing 190 (e.g., a lens, a grating, an emitting facet, etc.). In otherembodiments, the optical element 118 may be external to the PIC.

The receiver portion 120 of the PIC 100 is shown to include a receivingoptical element array 122, a receive coupler/array 124, and an array ofdetectors 126. The receiving optical element array 122 may be configuredby element design and/or layout for receiving light transmitted through,reflected by, and/or scattered by the media for sensing 190. The receivecoupler/array 124 may split (e.g., de-multiplex) the received light intoindividual wavelengths or wavelength groups.

The detector array 126 may be capable of detecting substantially all thewavelengths the light source array 112 (of the transmit portion 110 ofthe PIC 100)—i.e., able to emit and/or all the wavelengths of light tobe received from the media for sensing 190; the receive optical element122 may comprise a receive aperture that is substantially similar orlarger than the aperture of the transmit coupler array/aperture 116 (ofthe transmit portion 110 of the PIC 100). In other embodiments, detectormaterials of different semiconductor substrates may be used to detectall the light wavelengths. Furthermore, in some embodiments, separatedetectors may be used for different wavelengths, and a plurality ofdetectors, collecting apertures, and/or couplers may be used within thePIC 100.

Furthermore detecting weak scattered signals may be difficult in thepresence of strong source signals. In this embodiment,optical/thermal/electrical isolation components 135 are utilized forpreventing light from the light source array 112 from reaching thedetector array 126 (i.e., other than through the receive optical elementarray 122). These structures may be constructed, for example, by usingtrenches and metallic boundaries in the substrate of the PIC 100.

The PIC 100 may be used for spectroscopic processes (e.g., determiningaspects of an object based on the interaction of the object withelectromagnetic radiation, such as light). For example, spectroscopicmethods for noninvasive monitoring of blood constituents may benefitfrom techniques to resolve the scattering and/or absorption at differentor specific depths (coherent tomography) and also phase modulation forremoving “speckle” as well as measuring polarization rotation ofscattered light. In this embodiment, a delay line and phase modulator130 may be used to provide a delayed reference of the light source array112 incident of the detectors 126. In some embodiments, the detectors126 may comprise components for detecting the polarization components ofthe received light signals. FIG. 1C illustrates an embodiment whereinthe receive coupler/array 124C comprises polarization splitting elementsto split light by wavelength and by TE/TM polarization to be received bydetector array 126C. In some embodiments, by tuning the wavelengths ofthe outputs of the light source array 112 in time (e.g. swept source),the effective “distance” of the reference beam can be modified withoutusing moving parts.

Utilizing the PIC 100 for including both light emitter circuitry (e.g.,the transmitter portion 110) and light sensing circuitry (e.g., thereceiver portion 120), the size, weight, and power requirements of aspectrometer device may be reduced such that the device may be batterypowered and compatible with mobile or wearable devices. Additionally,solutions utilizing separate sources and detectors may use an opticalfiber bundle where the source light and scattered light could beemitted/collected in close proximity to each other. This fiber bundlingand coupling adds additional size and cost for the device, and is notused for the PIC 100. However, in other embodiments, the transmitterportion 110 and the receiver portion 120 may be included in differentPICs. Furthermore, by using lasers for the light source array 112, powerefficiency is increased (compared to an interferometer making use ofbroadband light) and light filtering elements may not need to beincluded in the receiver portion 120 of the PIC 100.

The PIC 100 may be formed of any semiconductor material suitable forphotonic devices and photonic operation, such as silicon-based materials(e.g., silicon (Si), silicon nitride (SiN)); non-silicon material suchas III-V material, magneto-optic material, or crystal substratematerial; or a combination of silicon and non-silicon material(alternatively referred to as “heterogeneous material”). The PIC 100 mayinclude one or more optical devices controlled and/or driven, at leastin part, by control and/or driver circuitry included in one or moreelectronic components. The electronic components may include one or moreapplication specific integrated circuits (ASICs), and may be formed ofany semiconductor material suitable for electronic devices andelectronic operation, such as Si.

At least some of the components of the PIC 100 can compriseheterogeneous material. In some embodiments, waveguides interconnectingthe optical components of PIC 100 may be formed in an SOI substrate. Thelight source array 112 may comprise a plurality of heterogeneous lasers,each laser formed from silicon material of the SOI substrate and to emitan output wavelength comprising an infrared wavelength. Each of theselasers may comprise a resonant cavity included in one of the pluralityof waveguides, and a gain material comprising a non-silicon material andadiabatically coupled to the respective waveguide. In some embodiments,the light source array may include lasers having different non-silicongain materials.

The PIC 100 can be closely integrated with electronics, for example bymounting an electrical chip and photonic chip to the same board, orfabricating electronics and photonics on the same chip. Due to closeintegration, radio frequency (RF) signals may be transmitted efficientlybetween electronic circuits and photonic transmitters and receivers. RFmodulation of light and phase sensitive detection may be used to improvethe signal to noise of the measurement and measure the optical delay thesignal has passed through, enabling extraction of the scattering andabsorption properties of the medium being measured (without priorassumptions of either of the properties).

FIG. 2A-FIG. 2B illustrate cross-section and top-down views ofcomponents of PICs used for optical sensing in accordance with someembodiments. A PIC is shown in a cross sectional view 200A and top-downview 200B to include an array of light sources 202. Light from the arrayof light sources 202 is received by an output coupler 204 via aplurality of waveguides 206. In some embodiments, the array of lightsources 202 are configured to emit a plurality of wavelength ranges. ThePIC 200 is further shown to include a plurality of detectors 211-215(each of which, in this embodiment, includes collection apertures).

As shown in this embodiment, the PIC 200 includes lenses 220-225. Thelens 220 is used for shaping the emitted light from the array of lightsources 202 (via the coupler 204) and directing the emitted lighttowards the media for sensing 290. The lenses 221-225 are used forshaping the light reflected from the media for sensing 290 and directingthe reflected light towards the detectors 211-215, respectively. In thisembodiment, the detectors 211-215 are shown to be surrounding thecoupler 204 and are shown to be placed (roughly) equidistant from thecoupler 204.

The PIC 200 is shown to emit incident light 230 and receive reflectedscattered light 235 (reflected/scattered by the media for sensing 290)normal to a surface of the PIC 200. Light directing elements such asgratings may be used to direct the light 230 and 235 normal to thesurface of the PIC 200 to reduce the size of the device.

Furthermore, scanning the incident light 230 parallel to the surface ofthe media for sensing 290 may remove noise associated with movement ofthe media. In some embodiments, elements for scanning the input to thetransmit coupler 204 may be used to modify the angle of emission of theincident light 230 (e.g., a sweeper incident on a grating coupler orcurved 45 degree mirror). In these embodiments, 2D scanning may befacilitated, for example, by splitting the source signal in two sweepersand combining them in polarization combining coupler or using twoorthogonal output couplers.

Other embodiments for scanning the incident light 230 parallel to thesurface of the media for sensing 290 may use lenses that have dynamicfocal and tilt properties (e.g., liquid lenses). In these embodiments,the lens properties can be adjusted to compensate for dispersiveproperties of a grating coupler or to enhance them for scanning theoutput beam angle.

In some embodiments, the multiple detectors 211-215 may be used toremove speckle by collecting the reflected scattered light 235 atdifferent angles, an approach referred to herein as angular compounding.Additionally, speckle may be removed by using the multiple lenses221-225 to collect light emitted from the media for sensing 290 atdifferent anglesThe position of the detectors may also vary based on theintended use of the device. A PIC is shown in a cross sectional view250A and a top-down view 250B of FIG. 2B to include the same componentsas the PIC 200; however, in this embodiment, some of the collectionapertures and detectors 211-214 of the PIC 250 are located at differentdistances from the source of the incident light (i.e., the coupler 204).This layout of the detectors 211-214 may aid in the acquisition ofscattering and absorption properties of the medium for sensing 290.

FIG. 3 illustrates a cross-sectional view of components of a PIC usedfor optical sensing in accordance with some embodiments. A PIC 300 isshown in a cross sectional view to include one or more light sources302. Light from the one or more light sources 302 is received by agrating 304 to direct light towards a media for sensing 390. The PIC 300is further shown to include gratings 306 associated with a plurality ofdetectors to detect light reflected from the media for sensing 390.

In this embodiment, scattered or reflected light from the media forsensing 390 may be collected by the same aperture and coupler from whichthe light source was coupled out of the PIC—illustrated in thisembodiment as lens 320. The gratings 304 and 306 are placed under thelens 320 (i.e., a single aperture) in order to accomplish one or moretechnical effects, including covering several different spectral rangesthat cannot be covered by a single grating, collecting light at severalgratings in order to average out speckle in a interferometricmeasurement, and/or improving signal-to-noise ratio. Furthermore, inother embodiments, light may be emitted from a light source andcollected by a collector via a same grating.

FIG. 4 is a flow diagram of a process for operating an optical sensingdevice in accordance with some embodiments. Flow diagrams as illustratedherein provide examples of sequences of various process actions.Although the actions are shown in a particular sequence or order, unlessotherwise specified, the order of the actions can be modified. Thus, thedescribed and illustrated implementations should be understood only asexamples. The illustrated actions can be performed in a different order,and some actions can be performed in parallel. Additionally, one or moreactions can be omitted in various embodiments; thus, not all actions arerequired in every implementation. Other process flows are possible.

A process 400 is illustrated as including an operation that is executedto tune a light source array of a spectroscopic sensing device (shown asblock 402). In some embodiments, the light source array may comprisetuning elements, such as a tunable filter, for tuning the output of thelight source array to emit over one or more wavelength ranges (e.g.,infrared wavelength ranges). In some embodiments, by tuning thewavelengths of the outputs of the light source array in time (e.g. sweptsource), the effective “distance” of the reference beam can be modifiedwithout using moving parts.

An operation is executed to modulate the outputs of the light sourcearray (shown as block 404). In some embodiments, the outputs of thelight source array may be modulated at different carrier frequenciessuch that their individual contributions are more easily detectable.

The modulated output of the light source array is then directed towardsa media for sensing (shown as block 406). Spectroscopic sensing devicesare often used for detecting characteristics of organic matter such ashuman tissue, but these devices may also be used for any other objects.Light either reflected by or transmitted through the media for sensingis collected by one or more collector apertures (shown as block 408) andsubsequently received by one or more detectors (shown as block 410). Avariety of detection process can be used to detect characteristics ofthe media for sensing. For example, where coherent detection isutilized, the light collected from the media for sensing is combinedwith a component of light from one or more of the light sources that hasnot been coupled off of the PIC.

A delayed reference of the light source array incident of the one ormore detectors is provided to the light source array (shown as block412). This may be used for resolving the scattering and/or absorption atdifferent or specific depths (e.g., coherent tomography) and also phasemodulation for removing “speckle” as well as measuring polarizationrotation of scattered light (where the light collected has undergonescattering within the media for sensing). These operations formonitoring the power of the light sources to provide a reference for thereceived spectroscopic signal may be useful as semiconductor sourcesdegrade in efficiency over time (as opposed to light detectors, which donot degrade).

FIG. 5 is an illustration of an arrayed waveguide grating (AWG) used foran optical sensing device in accordance with some embodiments. An AWG500 is shown to comprise a plurality of ports 501-504 and a port 505.When used to multiplex or combine light signals, input signals receivedvia the ports 501-504 are combined and output via the port 505 (in thisuse case, the ports 501-504 are coupled to light sources). When used tode-multiplex or separate light signals, an input signal receive via theport 505 is split into components by wavelength, which are then eachoutput via the ports 501-504 (in this use case, the ports 501-504 arecoupled to detectors). In both of these use cases, the relationshipbetween channel wavelength and the ports 501-504 may be described as thefree spectral range (FSR) of the AWG 500. In other words, an opticalchannel (e.g., comprising a narrow band of wavelengths) is coupledbetween the port 505 and one of the ports 501-504. The AWG 500 maycomprise a cyclic AWG that comprises a periodicity that corresponds withthe FSR.

In this embodiment, the ports 501-504 of the AWG 500 are shown to becoupled to light sources 511-514, respectively. In embodiments where theAWG 500 comprises a cyclic AWG, it may be used to multiplex orde-multiplex several wavelengths with a wide span by locking thewavelengths to passband channels of the AWG 500.

In some embodiments, the AWG 500 is used multiplex different spectrallines which are far apart (shown as spectral lines 521-524 of awavelength grid 520), especially if the width of the spectral line iscomparable to the FSR of the AWG. Likewise, the AWG 500 may be used as ade-multiplexer to separate light collected from a media for sensing bywavelength channel.

Reference throughout the foregoing specification to “one embodiment” or“an embodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present disclosure. Thus, appearancesof the phrases “in one embodiment” or “in an embodiment” in variousplaces throughout the specification are not necessarily all referring tothe same embodiment. Furthermore, the particular features, structures,or characteristics can be combined in any suitable manner in one or moreembodiments. In addition, it is to be appreciated that the figuresprovided are for explanation purposes to persons ordinarily skilled inthe art and that the drawings are not necessarily drawn to scale. It isto be understood that the various regions, layers, and structuresrepresented in the figures can vary in size and dimensions.

The above described embodiments can comprise silicon on insulator (SOI)or silicon-based (e.g., silicon nitride (SiN)) devices, or can comprisedevices formed from both silicon and a non-silicon material. Saidnon-silicon material (alternatively referred to as “heterogeneousmaterial”) can comprise one of III-V material, magneto-optic material,or crystal substrate material.

III-V semiconductors have elements that are found in group III and groupV of the periodic table (e.g., Indium Gallium Arsenide Phosphide(InGaAsP), Gallium Indium Arsenide Nitride (GaInAsN)). The carrierdispersion effects of III-V-based materials can be significantly higherthan in silicon-based materials, as electron speed in III-Vsemiconductors is much faster than that in silicon semiconductors. Inaddition, III-V materials have a direct bandgap which enables efficientcreation of light from electrical pumping. Thus, III-V semiconductormaterials enable photonic operations with an increased efficiency oversilicon for both generating light and modulating the refractive index oflight.

Thus, III-V semiconductor materials enable photonic operation with anincreased efficiency at generating light from electricity and convertinglight back into electricity. The low optical loss and high qualityoxides of silicon are thus combined with the electro-optic efficiency ofIII-V semiconductors in heterogeneous optical devices; in someembodiments, said heterogeneous devices utilize low-loss heterogeneousoptical waveguide transitions between the devices' heterogeneous andsilicon-only waveguides.

Magneto-optic materials allow heterogeneous PICs to operate based on themagneto-optic (MO) effect. Such devices can utilize the Faraday effect,in which the magnetic field associated with an electrical signalmodulates an optical beam, offering high bandwidth modulation, androtates the electric field of the optical mode, enabling opticalisolators. Said magneto-optic materials can comprise, for example,materials such as iron, cobalt, or yttrium iron garnet (YIG).

Crystal substrate materials provide heterogeneous PICs with a highelectro-mechanical coupling, linear electro optic coefficient, lowtransmission loss, and stable physical and chemical properties. Saidcrystal substrate materials can comprise, for example, lithium niobate(LiNbO₃) or lithium tantalate (LiTaO₃).

In the foregoing detailed description, the method and apparatus of thepresent subject matter have been described with reference to specificexemplary embodiments thereof. It will, however, be evident that variousmodifications and changes can be made thereto without departing from thebroader spirit and scope of the present inventive subject matter. Thepresent specification and figures are accordingly to be regarded asillustrative rather than restrictive.

In some embodiments, a PIC may comprise a plurality of waveguides formedin a silicon on insulator (SOI) substrate, and a plurality ofheterogeneous lasers, each laser formed from a silicon material of theSOI substrate and to emit an output wavelength comprising an infraredwavelength. Each of these lasers may comprise a resonant cavity includedin one of the plurality of waveguides, and a gain material comprising anon-silicon material and adiabatically coupled to the respectivewaveguide. A light directing element may direct outputs of the pluralityof heterogeneous lasers from the PIC towards an object, and one or moredetectors may detect light from the plurality of heterogeneous lasersreflected from or transmitted through the object.

In some embodiments, the one or more detectors and the light directingelement are both included in the PIC. In some embodiments, the PICfurther comprises one or more emission apertures to emit light from theplurality of heterogeneous lasers, and one or more collection aperturesto receive light for the one or more detectors. In some embodiments, aquantity of the plurality of collection apertures is greater than aquantity of the one or more emission apertures. In some embodiments, theone or more emission apertures and the one or more collection aperturescomprise a same single aperture. In some embodiments, at least two ofthe plurality of collection apertures are different distances from theone or more emission apertures.

In some embodiments, the light directing element comprises an edgeemitting facet to emit light from an edge of the PIC, and a tuningmirror to direct light from the edge emitting facet towards the object.In some embodiments, the light directing element comprises a grating. Insome embodiments, the light directing element is to direct the outputsof the plurality of heterogeneous lasers normal to a surface of the PIC.In some embodiments, the plurality of heterogeneous lasers areconfigured to emit a plurality of wavelength ranges, and the one or moredetectors comprise a detector for each wavelength range.

In some embodiments, the plurality of heterogeneous lasers comprises afirst laser having a gain material comprising a first non-siliconmaterial, and a second laser having a gain material comprising a secondnon-silicon material different than the first non-silicon material.

In some embodiments, the PIC further comprises one or more modulators tomodulate intensities of the outputs of the plurality of heterogeneous,the intensities to be modulated with a carrier frequency.

In some embodiments, the light collected from the object is coupled intoa waveguide mode. In some embodiments, the light collected from theobject is to be combined with a component of light from one or more ofthe heterogeneous lasers that has not been coupled off of the PIC.

Some embodiments described a spectroscopic sensing device comprising alight source array comprising a plurality of heterogeneous lasers, eachlaser formed from a silicon material and a non-silicon material, controlcircuitry to generate control signals to tune the light source array toemit output optical signals comprising infrared wavelengths over one ormore wavelength ranges, and modulate the output signals of the lightsource array, a light directing element to direct the modulated outputsignals of the light source array towards an object, and one or moredetectors to detect light reflected from or transmitted through theobject.

In some embodiments, the outputs of the light source array are modulatedat different carrier frequencies. In some embodiments, the lightdirecting element is to direct the modulated output signals of the lightsource array normal to a surface of the device. In some embodiments, theobject comprises human tissue. In some embodiments, the spectroscopicdevice further comprises a wearable housing to include the light sourcearray, the control circuitry, the light directing element, and the oneor more detectors.

The invention claimed is:
 1. A method of processing light from an objectusing a photonic integrated circuit, the method comprising: couplinglight into one or more waveguides formed in the photonic integratedcircuit, the light being generated at one or more wavelengths by a lightsource; directing the light towards a lens using a grating that iscoupled to the one or more waveguides; directing the light towards theobject using the lens; directing, with the lens, a portion of returninglight that is returned from the object onto at least one detector; andreceiving, with the at least one detector, at least the portion ofreturning light that is returned from the object.
 2. The method of claim1, wherein the light source is integrated in the photonic integratedcircuit.
 3. The method of claim 1, wherein the at least one detector iscoupled to a plurality of gratings to receive, from the lens, theportion of returning light that is returned from the object.
 4. Themethod of claim 3, wherein the plurality of gratings are located aroundthe grating that directs the light towards the lens.
 5. The method ofclaim 1, wherein the grating transmits the light towards the lens andreceives the returning light from the lens.
 6. The method of claim 1,wherein the grating is coupled to the detector that receives thereturning light that is returned from the object.
 7. The method of claim1, wherein the light source is a tunable light source.
 8. The method ofclaim 7, wherein the light is generated by the tunable light source at aplurality of wavelengths.
 9. The method of claim 7, wherein the lightsource comprises a light emitting diode and a tunable filter.
 10. Themethod of claim 7, wherein the light source comprises a tunable laser.11. The method of claim 1, further comprising: modulating the light fromthe light source with modulation frequencies that are different from oneanother.
 12. The method of claim 11, further comprising: analyzing asignal from the at least one detector at the modulation frequencies. 13.A photonic integrated circuit to process light from an object, thephotonic integrated circuit comprising: one or more waveguides formed inthe photonic integrated circuit, the one or more waveguides to propagatelight generated at one or more wavelengths by a light source; a gratingto direct the light towards a lens, the grating being coupled to the oneor more waveguides to receive the light from the light source; a lens todirect the light towards the object and direct a portion of returninglight that is returned from the object onto a detector; and a detectorto receive the portion of the light that is returned from the object.14. The photonic integrated circuit of claim 13, wherein the lightsource is integrated in the photonic integrated circuit.
 15. Thephotonic integrated circuit of claim 13, further comprising: a pluralityof gratings to receive, from the lens, the portion of the returninglight that is returned from the object.
 16. The photonic integratedcircuit of claim 15, wherein the plurality of gratings are locatedaround the grating that directs the light towards the lens.
 17. Thephotonic integrated circuit of claim 13, wherein the grating transmitsthe light towards the lens and receives the returning light from thelens.
 18. The photonic integrated circuit of claim 13, wherein the lightsource is a tunable light source.
 19. The photonic integrated circuit ofclaim 18, wherein the light source comprises a light emitting diode anda tunable filter.
 20. The photonic integrated circuit of claim 18,wherein the light source comprises a tunable laser.